The present invention relates to a method and device for abrading the skin. More particularly, the invention is directed to a method of abrading the stratum corneum to promote transdermal delivery or sampling of a substance.
The skin is made up of several layers with the upper composite layer being the epithelial layer. The outermost layer of the skin is the stratum corneum that has well known barrier properties to prevent external molecules and various substances from entering the body and internal substances from exiting the body. The stratum corneum is a complex structure of compacted keratinized cell remnants having a thickness of about 10-30 microns. The stratum corneum forms a hydrophobic membrane to protect the body from invasion by various substances and to prevent the outward migration of various compounds.
The natural impermeability of the stratum corneum inhibits the administration of most pharmaceutical agents and other substances through the skin. Numerous methods and devices have been proposed to enhance the permeability of the skin and to increase the diffusion of various drugs through the skin so that the drugs can be utilized by the body. Typically, the delivery of drugs through the skin is enhanced by either increasing the permeability of the skin or increasing the force or energy used to direct the drug through the skin.
Several methods of enhancing skin permeability have been proposed and used with varying success. The prior mechanical methods use an adhesive strip that is repeatedly applied to the skin to strip numerous layers of cells from the stratum corneum. Other methods use a scraper such as a scalpel blade or sandpaper to abrade the skin. These methods are usually painful or uncomfortable and increase the risk of infection by excessively reducing the skin barrier function.
Other methods of increasing skin permeability use various chemical permeation enhancers or electrical energy such as electroporation. Ultrasonic energy such as sonophoresis and laser treatments has been used. These methods require complex and energy intensive electronic devices that are relatively expensive. The chemical enhancers are often not suitable for transdermal drug delivery or sampling.
One example of a method for increasing the delivery of drugs through the skin is iontophoresis. Iontophoresis generally applies an external electrical field across the skin. Ionic molecules in this field are moved across the skin due to the force of the electric field. The amount and rate of drug delivery using iontophoresis can be difficult to control. Iontophoresis can also cause skin damage on prolonged exposure.
Sonic, and particularly ultrasonic energy, has also been used to increase the diffusion of drugs through the skin. The sonic energy is typically generated by passing an electrical current through a piezoelectric crystal or other suitable electromechanical device. Although numerous efforts to enhance drug delivery using sonic energy have been proposed, the results generally show a low rate of drug delivery.
Another method of delivering drugs through the skin is by forming micropores or cuts through the stratum corneum. By piercing the stratum corneum and delivering the drug to the tissue below the stratum corneum, many drugs can be effectively administered. The devices for piercing the stratum corneum generally include a plurality of micron-size needles or blades having a length to pierce the stratum corneum without passing completely through the epidermis. Examples of these devices are disclosed in U.S. Pat. No. 5,879,326 to Godshall et al.; U.S. Pat. No. 5,250,023 to Lee et al.; and WO 97/48440.
Transdermal drug delivery is also known to use pulsed laser light to ablate the stratum corneum without significant ablation or damage to the underlying epidermis. A drug is then applied to the ablated area and allowed to diffuse through the epidermis.
The prior methods and apparatus for the transdermal administration of drugs have exhibited limited success. Accordingly, a continuing need exists in the industry for an improved device for the transdermal administration of various drugs and other substances.
The present invention is directed to a method and device for abrading the skin, and particularly, the stratum corneum of the skin. The invention is further directed to a method of obtaining a sample or for the transdermal delivery of a substance, such as a drug or pharmaceutical agent, through the abraded area on the stratum corneum. One aspect of the invention is directed to a method and device for preparing a delivery site on the skin to enhance the delivery of a pharmaceutical agent through the stratum corneum of the skin to a sufficient depth where the pharmaceutical agent can be absorbed and utilized by the body.
To clarify this invention, two definitions are made. Penetrate, in the context of this invention, shall mean to enter, but not pass through a body or substrate. Pierce, in the context of this invention, shall mean to enter and pass through the body or substrate
Accordingly, a primary object of the invention is to provide a method and device for efficiently penetrating the stratum corneum substantially without pain to the patient and with a minimum of irritation to skin, thereby exposing the tissue below the stratum corneum directly to a pharmaceutical agent for absorption by the body.
A further object of the invention is to provide a method for abrading the stratum corneum in a simple and reliable manner.
Another object of the invention is to provide a microabrader device having a plurality of microneedles which when rubbed on the skin penetrate the stratum corneum and form a plurality of spaced-apart grooves in the stratum corneum.
A further object of the invention is to provide a device for delivering a plurality of drugs transdermally through an abraded area of the skin to a patient either simultaneously or sequentially.
Another object of the invention is to provide a method for transdermally delivering a substance through an abraded area of the skin using iontophoresis.
A further object of the invention is to provide a method and device for penetrating the stratum corneum and for the sampling of a substance from a patient.
A still further object of the invention is to provide a device having a plurality of microneedles for abrading and penetrating the stratum corneum and a supply for supplying a substance, such as a pharmaceutical agent, to the microneedles.
Another object of the invention is to provide a device having a plurality of microneedles having a blunt tip for abrading a plurality of grooves into the stratum corneum without piercing the stratum corneum.
Still another object of the invention is to provide an abrader and delivery device having an array of microneedles for abrading and penetrating the stratum corneum of the skin, where the device has a channel in a bottom surface for directing a substance to the microneedles and the abraded skin.
A further object of the invention is to provide a microabrader device having an array of microneedles for abrading the skin to transdermally withdraw a substance from the patient.
A further object of the invention is to provide a method and device for reducing the impedance of the skin without piercing the stratum corneum for measuring the body""s internal electrical signals, such as EKG.
These and other objects of the invention are substantially achieved by providing a device for abrading the skin to promote the delivery or withdrawal of a substance through the skin of a patient. In a preferred embodiment, the device comprises a planar support having a bottom surface. A plurality of microneedles is coupled to and integral with the bottom surface of the support. The microneedles have a blunt, flat tip and a length sufficient to penetrate the stratum corneum of the skin without piercing the stratum corneum during abrading of the skin to enhance the permeability of the skin.
The objects and advantages of the invention are further attained by providing a method for intradermal delivery of a substance to a patient. The method comprises positioning a microabrader at a delivery site on the skin of a patient where the microabrader has a planar support and a plurality of microneedles coupled to the planar support. The microneedles have a length to penetrate the stratum corneum of the skin without piercing the stratum corneum. The microabrader is moved over the surface of the skin to abrade the stratum corneum on the delivery site and thereafter a substance is applied to the delivery site for transferring through the skin for absorption by the body.
The objects of the invention are further attained by providing a method of treating the skin of a patient to enhance transdermal delivery of a substance or the withdrawal of a substance from the body. The method comprises positioning a microabrader with a plurality of microneedles at a delivery site on the skin of the patient and moving the microabrader in a direction to abrade the stratum corneum and form an abraded area. The abraded area has a plurality of grooves formed in the skin by abrasion with the microneedles and a peak between the grooves. The grooves penetrate, but do not pass through or pierce the stratum corneum.
The objects, advantages and other salient features of the invention will become apparent from the following detailed description which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the invention.